Solar powered systems and methods for generating hydrogen gas and oxygen gas from water

ABSTRACT

Solar-powered systems and methods of generating hydrogen gas and oxygen gas from water are described. A solar-powered system for generating hydrogen gas and oxygen gas from water includes an electrolysis unit, a first generator unit, and a solar-powered turbine unit. The electrolysis unit is powered by the first generator unit. The solar-powered turbine unit is configured to drive the first generator unit and to supply steam to the electrolysis unit. The solar-powered turbine unit includes a first turbine coupled to and configured to provide shaft work to the first generator unit, a steam generation unit coupled to the steam feed inlet of the electrolysis unit and configured to hold water; and a solar unit configured to generate and provide heat to the steam generation unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit to U.S. Provisional Application No.62/106,056 titled “SOLAR POWERED SYSTEMS AND METHODS FOR GENERATINGHYDROGEN GAS AND OXYGEN GAS FROM WATER”, filed Jan. 21, 2015. The entirecontents of the above-referenced application is incorporated byreference without disclaimer.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The invention generally concerns a solar-powered system for generatinghydrogen gas and oxygen gas from water. In particular, the inventionrelates to such a system that utilizes a solar powered turbine unitcoupled to a generator and an electrolysis unit.

B. Description of Related Art

Hydrogen (H₂) gas is a valuable product and is used as a feed stock inpetroleum, chemical, energy and semiconductor industries. For example,hydrogen is used in the processing of hydrocarbons (for example,hydrocracking, hydrodealkylation, and hydrodesulfurization processes),the production of ammonia, the production of methanol, various chemicalprocesses (for example, hydrogenation reactions), and as a coolant.Hydrogen gas can be recovered as a by-product of chemical or biologicalreactions, or separated from production of fossil fuels. Conventionalmethods to produce hydrogen include steam reforming of natural gas,thermochemical splitting of water, and electrolysis of water. Hydrogenproduction as a product of water-splitting offers enormous potentialbenefits for the energy sector, the environment, and the chemicalindustry. These processes suffer from the problem that they can generatea large amount of carbon dioxide (CO₂) either from the chemical reactionor from the consumption of electricity derived from fossil fuel. Forexample, in steam reforming reactions, CO₂ can be generated as areaction product when excess water is used as shown in equation (I).

CH₄+2H₂O→CO₂+4H₂  (I)

Other processes that generate hydrogen require electrical energy whichgenerates CO₂ through the combustion of fossil fuel as illustrated inequation (II).

CH₄+2O₂→CO₂+2H₂O  (II)

Carbon dioxide is recognized by government agencies as the primarygreenhouse gas produced through human activity and the emission ofcarbon dioxide is regulated by many governmental agencies.

Conventional systems and methods attempt to reduce the carbon dioxideproduction through the use of solar energy. U.S. Patent ApplicationPublication No. 20130234069 describes solar receivers to generateelectricity for an electrolysis unit, and then use the heat rejectedfrom the electrolysis process as a heat source for the working fluid tobe used elsewhere in the power cycle. U. S. Patent ApplicationPublication No. 20120171588 to Fan et al. describes the use of solarenergy to power a reforming/water splitting block. These systems are notself-sufficient, however, suffer from reliance on carbon-basedfeedstocks or fuel to meet the energy requirements for their systems.

SUMMARY OF THE INVENTION

A solution to the problems of producing energy with minimal amount ofcarbon dioxide production (i.e., a low carbon dioxide footprint) hasbeen discovered. In particular, the solution resides in the ability toeliminate the use of fossil fuel as a source of electricity during theelectrolysis of water to generate hydrogen and oxygen. The chemicalreaction of water-splitting is shown in Equation (III).

2H₂O→2H₂+O₂  (III)

Notably, the invention is capable of elevating the temperature andpressure of the water, which can then be used in an electrolysis unit.By elevating the water temperature and pressure the overall electricalenergy needed for the water splitting reaction is reduced, which incertain aspects, can be at the expense of using additional heat inputfrom either solar energy or internal heat dissipation. The electricalenergy is produced using a generator that is coupled to a solar poweredturbine unit capable of driving the generator unit and providing steamto the electrolysis unit. This can be done without the use of fossilfuel and without producing carbon dioxide during the water-splittingreaction (see Equation (III) above and compare with Equations (I) and(II)).

In one particular aspect of the invention, a solar-powered system forgenerating hydrogen gas and oxygen gas from water is described. Thesystem can include (a) an electrolysis unit configured to producehydrogen gas and oxygen gas from water, (b) a first generator unitconfigured to provide electricity to the electrolysis unit; and (c) asolar-powered turbine unit configured to drive the first generator unitand to supply steam to the steam feed inlet. In a particular aspect, thesystem includes an air supply unit that feeds compressed air to theoxygen evolution side of the electrolysis unit to maintain less thanpure oxygen in the outlet stream. A non-limiting example of an airsupply unit is an air compressor. The electrolysis unit can include asteam feed inlet and at least a first product outlet for hydrogen gas oroxygen gas, or both. In a preferred aspect, the hydrogen gas and theoxygen gas exits the electrolysis unit as separate streams through twoproduct outlets. The oxygen gas can through a second product outlet andthe hydrogen gas can exit through the first product outlet. In aparticular aspect, the stream exiting the second product outlet is anoxygen-rich stream that includes oxygen and air. The solar-poweredturbine unit can include (i) a first turbine coupled to and configuredto provide shaft work to the first generator unit; (ii) a steamgeneration unit coupled to the steam feed inlet of the electrolysis unitand configured to hold water; and (iii) a solar unit configured togenerate and provide heat to the steam generation unit. In some aspectsof the invention, the solar unit is configured to generate and provideheat to the working fluid of the turbine. The steam produced by thesteam generation unit can include pressurized steam. Notably, carbondioxide is not produced in the water splitting reaction (see Equation(III)), thereby reducing or eliminating carbon dioxide production whenthe system is in use. The produced hydrogen gas, oxygen gas, or both caneach be used in a downstream chemical process. In a preferred aspect,both the produced hydrogen gas and the oxygen gas are used in adownstream chemical process. In some aspects of the invention, thesystem can also include a product cooling unit coupled to theelectrolysis unit and configured to receive and reduce the temperatureof the produced hydrogen gas or oxygen gas, or both. In a preferredaspect, the system can also include a product cooling unit coupled tothe electrolysis unit and configured to receive and reduce thetemperature of the produced hydrogen gas and oxygen gas. The productcooling unit can include (i) a second turbine coupled to and configuredto provide power to a second generator unit, wherein the second turbineis configured to receive the produced hydrogen gas or oxygen gas, orboth; and (ii) a heat transfer unit coupled to and configured totransfer heat produced from the product cooling unit to the steamgenerator unit. The second generator unit can be configured to provideelectricity to the electrolysis unit. In some aspects, the productcooling unit includes a third turbine coupled to and configured toprovide power to the second generator unit or to a third generator unit,wherein the third turbine is configured to receive the produced hydrogengas or oxygen gas, or both, and wherein the third generator unit isconfigured to provide electricity to the electrolysis unit.

In some aspects of the invention, the solar powered turbine unit caninclude (i) the first turbine coupled to and configured to provide shaftwork to the first generator unit; (ii) the steam generation unit coupledto the steam feed inlet of the electrolysis unit, (iii) the solar unitconfigured to generate and provide heat to the steam generation unit;and (iv) a condenser. The steam generation unit can include a boilerthat is configured to hold water and produce steam. The boiler can becoupled to the first turbine and configured to transfer the producedsteam from the boiler to the first turbine. The first turbine can becoupled to the condenser and configured to transfer steam from theturbine to the condenser. The condenser can be configured to condensethe steam transferred from the turbine into liquid, and be coupled toand configured to transfer the liquid to the boiler.

In some aspects of the invention, the solar powered turbine unit is aclosed-loop gas turbine unit that can include (i) the first turbinecoupled to and configured to provide shaft work to the first generatorunit; (ii) the steam generation unit coupled to the steam feed inlet ofthe electrolysis unit, and (iii) the solar unit configured to generateand provide heat to a cooled fluid (for example, a gas) produced fromthe steam generation unit. The steam generation unit can include a firstheat exchanger coupled to the first turbine to receive heated fluid fromthe first turbine. Heat can be transferred in the first heat exchangerfrom the heated fluid to water to produce steam and cooled fluid. Theheat exchanger can also be coupled to a compressor and configured totransfer the cooled fluid to the compressor. The compressor can becoupled to a second heat exchanger that is configured to heat the cooledfluid with heat produced by the solar unit. The second heat exchangercan be coupled to the first turbine to transfer the heated fluid to thefirst turbine. In some aspects of the invention the closed-loop gasturbine unit includes a back pressure steam turbine unit coupled to thefirst heat and configured to receive heat from the first heat exchanger.The back pressure steam turbine can include a fourth turbine couple toand configured to provide shaft work to the first generator unit. Insome instances of the present invention, the first turbine and thefourth turbine are set-up in series of another. In other aspects of theinvention, the back pressure steam turbine unit can include a fourthturbine coupled to and configured to provide power to a fourth generatorunit in which the fourth generator unit is configured to provideelectricity to the electrolysis unit.

Methods of generating hydrogen gas and oxygen gas from water using thesystems described throughout this specification are described. Themethods can include subjecting water to electrolysis conditionssufficient to produce hydrogen gas and oxygen gas, preferably asseparate streams. The hydrogen gas can be separated from the oxygen gas.The hydrogen gas, the oxygen gas, or both can be provided to one or morestorage units, chemical process units, transportation units, or anycombination thereof.

In the context of the present invention, twenty-one (21) embodiments aredescribed. Embodiment 1 includes a solar-powered system for generatinghydrogen gas and oxygen gas from water. The system can include (a) anelectrolysis unit configured to produce hydrogen gas and oxygen gas fromwater, the electrolysis unit can include a steam feed inlet and at leasta first product outlet for hydrogen gas, oxygen gas or both; (b) a firstgenerator unit configured to provide electricity to the electrolysisunit; and (c) a solar-powered turbine unit configured to drive the firstgenerator unit and to supply steam to the steam feed inlet, thesolar-powered turbine unit that includes (i) a first turbine coupled toand configured to provide shaft work to the first generator unit; (ii) asteam generation unit coupled to the steam feed inlet of theelectrolysis unit and configured to hold water; and (iii) a solar unitconfigured to generate and provide heat to the steam generation unit.Embodiment 2 is the system of embodiment 1, further including a productcooling unit coupled to the electrolysis unit and configured to receiveand reduce the temperature of the produced hydrogen gas or oxygen gas,or, preferably, both. Embodiment 3 is the system of embodiment 2,wherein the product cooling unit that includes (i) a second turbinecoupled to and configured to provide power to a second generator unit,wherein the second turbine is configured to receive the producedhydrogen gas or oxygen gas, or, preferably, both; and (ii) a heattransfer unit coupled to and configured to transfer heat produced fromthe product cooling unit to the steam generator unit. Embodiment 4 isthe system of embodiment 3, wherein the second generator unit isconfigured to provide electricity to the electrolysis unit. Embodiment 5is the system of embodiment 4, wherein the product cooling unit includesa third turbine coupled to and configured to provide power to the secondgenerator unit or to a third generator unit, wherein the third turbineis configured to receive the produced hydrogen gas or oxygen gas, or,preferably, both, and wherein the third generator unit is configured toprovide electricity to the electrolysis unit. Embodiment 6 is the systemof any one of embodiments 1-5, wherein the solar powered turbine unitcan include (i) the first turbine coupled to and configured to provideshaft work to the first generator unit; (ii) the steam generation unitcoupled to the steam feed inlet of the electrolysis unit, wherein thesteam generation unit includes a boiler that is configured to hold waterand produce steam; (iii) the solar unit configured to generate andprovide heat to the boiler; and (iv) a condenser; wherein the boiler iscoupled to the first turbine and configured to transfer steam from theboiler to the first turbine, wherein the first turbine is coupled to thecondenser and configured to transfer steam from the turbine to thecondenser, wherein the condenser is configured to condense the steamtransferred from the turbine into liquid, and wherein the condenser iscoupled to and configured to transfer the liquid to the boiler.Embodiment 7 is the system of any one of embodiments 1-5, wherein thesolar powered turbine unit is a closed-loop gas turbine unit thatincludes (i) the first turbine coupled to and configured to provideshaft work to the first generator unit; (ii) the steam generation unitcoupled to the steam feed inlet of the electrolysis unit, wherein thesteam generation unit can include a first heat exchanger coupled to thefirst turbine to receive heated fluid from the first turbine, whereinheat is transferred in the first heat exchanger from the heated fluid towater to produce steam and cooled fluid; and (iii) the solar unitconfigured to generate and provide heat to the cooled fluid; and whereinthe heat exchanger is coupled to a compressor and configured to transferthe cooled fluid to the compressor, wherein the compressor is coupled toa second heat exchanger that is configured to heat the cooled fluid withheat produced by the solar unit, and wherein the second heat exchangeris coupled to the first turbine to transfer the heated fluid to thefirst turbine. Embodiment 8 is the system of embodiment 7, furtherincluding a back pressure steam turbine unit. Embodiment 9 is the systemof embodiment 8, wherein the back pressure steam turbine is coupled tothe first heat exchanger and configured to receive steam from the heatexchanger. Embodiment 10 is the system of embodiment 9, wherein the backpressure steam turbine unit can include a fourth turbine coupled to andconfigured to provide shaft work to the first generator unit. Embodiment11 is the system of embodiment 9, wherein the back pressure steamturbine unit can include a fourth turbine coupled to and configured toprovide power to a fourth generator unit, and wherein the fourthgenerator unit is configured to provide electricity to the electrolysisunit. Embodiment 12 is the system of any one of embodiments 1 to 11,wherein the steam produced by the steam generation unit is pressurizedsteam. Embodiment 13 is the system of any one of embodiments 1 to 12,wherein the system does not produce carbon dioxide during use.Embodiment 14 is the system of any one of embodiments 1 to 13, whereinthe produced hydrogen gas or the produced oxygen gas, or both, are eachused in a downstream chemical process. Embodiment 15 is the system ofany one of embodiments 1 to 14, wherein the electrolysis unit caninclude at least two product outlets, wherein the first product outletis for hydrogen gas and a second product outlet is for oxygen gas.Embodiment 16 is the system of embodiment 15, further can include an airsupply coupled to the electrolysis unit, wherein the air supply providesair to an oxygen evolution side of the electrolysis unit such that amixture of oxygen and air are produced from the second outlet.

Embodiment 17 is a method of generating hydrogen gas and oxygen gas fromwater with any one of the systems of embodiments 1 to 16. The method caninclude subjecting water to electrolysis conditions sufficient toproduce hydrogen gas and oxygen gas. Embodiment 18 is the method ofembodiment 17, further including providing the hydrogen gas to one ormore storage units, chemical process units, transportation units, or anycombination thereof. Embodiment 19 is the method of any one ofembodiments 17 to 18, further including providing the oxygen gas to oneor more storage units, chemical process units, transportation units, orany combination thereof. Embodiment 20 is the method of any one ofembodiments 17 to 19, wherein the produced hydrogen gas or the producedoxygen gas, or both, are each used in a downstream chemical process.Embodiment 21 is the method of any one of embodiments 17 to 20, whereinno carbon dioxide is produced by the system. Embodiments 22 is themethod of any one of embodiments 17 to 21, wherein the water is in theform of steam produced by the steam generation unit.

The following includes definitions of various terms and phrases usedthroughout this specification.

The term “coupled” means either a direct connection or an indirectconnection (for example, one or more intervening connections) betweenone or more objects or components, and not necessarily mechanically; twoitems that are “coupled” may be unitary with each other.

The term “fluid” refers to a substance or a mixture of compounds thatexist in a gas phase, liquid phase, or a mixture thereof and are capableof flowing. Non-limiting examples of a fluid include air, liquid carbondioxide, gaseous carbon dioxide, water, steam, or mixtures thereof.

The term “about” or “approximately” are defined as being close to asunderstood by one of ordinary skill in the art, and in one non-limitingembodiment the terms are defined to be within 10%, preferably within 5%,more preferably within 1%, and most preferably within 0.5%.

The term “substantially” and its variations are defined as being largelybut not necessarily wholly what is specified as understood by one ofordinary skill in the art, and in one non-limiting embodimentsubstantially refers to ranges within 10%, within 5%, within 1%, orwithin 0.5%.

The terms “inhibiting” or “reducing” or “preventing” or “avoiding” orany variation of these terms, when used in the claims and/or thespecification includes any measurable decrease or complete inhibition toachieve a desired result.

The term “effective,” as that term is used in the specification and/orclaims, means adequate to accomplish a desired, expected, or intendedresult.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims or the specification may mean “one,” but itis also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.”

The words “comprising” (and any form of comprising, such as “comprise”and “comprises”), “having” (and any form of having, such as “have” and“has”), “including” (and any form of including, such as “includes” and“include”) or “containing” (and any form of containing, such as“contains” and “contain”) are inclusive or open-ended and do not excludeadditional, unrecited elements or method steps.

The systems of the present invention can “comprise,” “consistessentially of,” or “consist of” particular ingredients, components,compositions, etc. disclosed throughout the specification. With respectto the transitional phase “consisting essentially of,” in onenon-limiting aspect, a basic and novel characteristic of the systems ofthe present invention are their use of solar energy and the reducedamount of carbon dioxide produced when the system is in use.

Other objects, features and advantages of the present invention willbecome apparent from the following figures, detailed description, andexamples. It should be understood, however, that the figures, detaileddescription, and examples, while indicating specific embodiments of theinvention, are given by way of illustration only and are not meant to belimiting. Additionally, it is contemplated that changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and B are schematics of a solar-powered system of the presentinvention for generating hydrogen gas and oxygen gas from water.

FIG. 2 is a schematic of a solar-powered turbine unit of the presentinvention.

FIG. 3 is a schematic of the solar-powered system of the presentinvention that includes a cooling unit.

FIG. 4 is a schematic of the solar-powered turbine unit of the presentinvention that includes a boiler and a condenser.

FIG. 5 is a schematic of the solar-powered turbine unit of the presentinvention that includes a closed-loop gas turbine unit.

FIG. 6 is a schematic of the solar-powered turbine unit of the presentinvention that includes a closed-loop gas turbine unit and aback-pressure steam turbine unit set-up in series with one another.

FIG. 7 is a schematic of the solar-powered turbine unit of the presentinvention that includes a closed-loop gas turbine unit and aback-pressure steam turbine unit and a fourth generator unit set-up inparallel with one another.

FIG. 8 is a schematic of the solar-powered turbine unit of the presentinvention that includes a closed-loop gas turbine unit.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Thedrawings may not be to scale. It should be understood that the drawingsand detailed description thereto are not intended to limit the inventionto the particular form disclosed, but to the contrary, the intention isto cover all modifications, equivalents and alternatives falling withinthe spirit and scope of the present invention as defined by the appendedclaims

DETAILED DESCRIPTION OF THE INVENTION

The currently available water-splitting systems require a significantamount of electrical energy. Most of the electrical energy is producedby combustion of fossil fuel, which produces carbon dioxide, a knowngreenhouse gas. By comparison, the present invention allows for reducedor limited carbon dioxide production by relying on the water-splittingreaction of Equation (III). The discovery lies in the combination ofsolar power, heat recovery, and steam generation to produce sufficientheat and electricity to power an electrolysis unit. Use of the steam inthe electrolysis unit reduces the electrical energy needed for the watersplitting reaction compared to the electrical energy required when usingan electrolysis unit operating at or near ambient temperature fed withwater.

These and other non-limiting aspects of the present invention arediscussed in further detail in the following sections with references toFIGS. 1-7. In FIGS. 1-7, mechanical or thermal energy is depicted usinga line with an open-headed arrow. Mass flow is depicted with a line anda closed-headed arrow. Electrical power is depicted with a dashed lineand a closed-headed arrow. It should be understood that inlets, outlets,valves and connectors are known to one of ordinary skill.

A. Solar-Powered System for Generating Hydrogen Gas and Oxygen Gas fromWater

FIGS. 1A and 1B are schematics that depict a solar-powered system of thepresent invention. The solar-powered system 100 can include anelectrolysis unit 102, a first generator unit 104, and a solar-poweredturbine unit 106. Steam feed 108 generated in the solar-powered turbineunit 106 can exit the solar-powered turbine unit 106 and enter theelectrolysis unit 102. The use of steam instead of water in electrolysisunit 102 lowers the amount of electrical energy required for theelectrolytic water-splitting reaction as compared to room temperatureelectrolytic water-splitting conditions. The steam feed may be deliveredto the electrolysis unit 102 at a pressure of 1 to 10 bar or 10 bar. Inelectrolysis unit 102, the steam is split into hydrogen gas and oxygengas. Electrolysis unit 102 can be a high steam temperature electrolysisunit. In a preferred embodiment, electrolysis unit 102 can be a solidoxide electrolysis system using a solid electrolyte of one or morematerials such as, for example, yttria-stabilised zirconia, scandiastabilized zirconia, ceria-based electrolytes, or lanthanum gallatematerials. Electrolysis conditions sufficient to split water intohydrogen and oxygen can include temperatures of 50 to 1000° C., 250 to950° C., or from 600 to 900° C. and pressures of 0.1 to 1 MPa. Hydrogengas stream 110 can exit electrolysis unit 102 and be used in downstreamchemical process, transportation units. Oxygen gas stream 112 can exitelectrolysis unit 102 and be used in downstream chemical process and/ortransportation units. The hydrogen gas stream and/or oxygen gas streamcan also be stored, transported, or sold. Electrolysis unit 102 iscapable of converting 50 to 90 mol % water to hydrogen gas and oxygengas. In some embodiments, hydrogen gas and oxygen gas generated duringwater splitting can be collected in a hydrogen collector and an oxygencollector in the electrolysis unit 102. The collectors can each providehydrogen gas or oxygen gas to downstream units, transportation units,storage units, or the like.

As shown in FIG. 1B, air supply unit 114 is coupled to electrolysis unit102. Air supply unit 114 can provide air stream 116 (for example,compressed air) to the oxygen evolution side of the electrolysis unit tomaintain less than pure oxygen in the outlet stream. The air enteringelectrolysis unit 102 can be compressed air. In some embodiments, theoxygen stream 112 exiting electrolysis unit is an oxygen-rich streamhaving at least 10 to 90 vol % oxygen, 50 to 80 vol % oxygen, or 60 to70 vol % oxygen.

In FIGS. 1A and 1B, first generator unit 104 is coupled to electrolysisunit 102 and solar-powered turbine unit 106. Solar-powered turbine unit106 can include a first turbine. The first turbine can be one or moresolar-powered gas turbine, steam turbines, back pressure steam turbinesor any combination thereof. Turbines in solar-powered turbine unitgenerate mechanical energy (shaft work), which is supplied to firstgenerator unit 104. First generator unit 104 uses the mechanical energyto generate and provide electrical energy 118 to electrolysis unit 102.Referring to FIG. 2, system 200 depicts a system to make hydrogen andoxygen gases from water that incorporates a steam turbine. Solar-poweredturbine unit 106 can include first turbine 200, solar heat collectionunit 202, and steam generation unit 204. First turbine 200 can providemechanical energy 120 to first generator 104. In FIG. 2, first turbine200 is a steam turbine. Solar heat collection unit 202 can generate andprovide heat 208 to the steam generation unit 204 as describedthroughout this specification. Solar heat collection unit 202 can be ahigh-temperature solar collector that includes a mirror and/or lenssystem (for example, a solar farm) for sunlight collection and iscapable of providing sufficient heat to heat water in to 300 to 1000° C.at 20 to 200 bar of pressure or air to temperatures of about 720 to1350° C. at 1 to 20 bar. In a preferred embodiment, the solar collectorsare computer controlled mirrors (e.g., heliostats) that orientthemselves according to the changing direction of the sunlight over thecourse of the day. Steam generator 204 is coupled to first turbine 200as described throughout this Specification. For example, when firstturbine 200 is a steam turbine, steam generator 204 may generate steamfeed 210 and steam feed 108. Steam feed 210 can be provided to the firstturbine, which generates mechanical energy 120 and reduced pressuresteam stream 212. In the steam generation unit 204, water 214 enterssteam generation unit 204 and can be pressurized and/or heated toproduce the steam feed 210.

B. Solar-Powered System with a Cooling Unit

In some aspects of the invention, a solar-powered system of the presentinvention can include a cooling unit. FIG. 3 depicts a schematic of thesolar-powered system 300 having solar-powered turbine unit 106 andelectrolysis unit 102 coupled to cooling unit 302. The cooling unit 302can include second turbine 304, second generator unit 306, third turbine308, third generator unit 310, and heat transfer unit 312. In anotheraspect of the invention, the electrolysis unit is fed with a compressedair stream 116 (See, for example FIG. 1B) that is used to sweep theoxygen produced at one of the electrodes of the electrolysis unit, toproduce an oxygen-rich gas stream 112. In system 300, hydrogen gasstream 110 can exit electrolysis unit 102 at a temperature of 800 to1000° C. and pressure of 1 to 10 bar, and be expanded in second turbine304. Expansion of hydrogen gas stream 110 in second turbine 304generates mechanical energy 316 and hot hydrogen gas stream 318.Generated mechanical energy 316 is provided to second generation unit306, which produces electrical energy 320 that is provided toelectrolysis unit 102. Electrical energy 320 can be used to powerelectrolysis unit 102 or other equipment such as, for example, airsupply unit 114. Hot hydrogen gas stream 118 can exit second turbine 304and undergo heat exchange in heat transfer unit 312 to form cooledhydrogen gas stream 322 and recovered heat energy 324. Recovered heatenergy 324 can be transferred to steam generation unit 106. Similarly,oxygen-rich gas stream 112 can exit electrolysis unit 102 having atemperature of 800 to 1000° C. and a pressure of to 10 bar, and beexpanded in third turbine 308. Expansion of the oxygen in the thirdturbine 308 generates mechanical energy 326 and hot oxygen-rich gasstream 328. Generated mechanical energy 326 is provided to thirdgeneration unit 310, which produces electrical power 330. Electricalpower 330 can be used to power the electrolysis unit 102 or otherequipment. In some embodiments, electrical power 320 and electricalpower 330 can enter electrolysis unit at the same inlet. It should beunderstood that the electrical power can be connected to theelectrolysis unit through one or more inlets. Hot oxygen-rich gas stream318 can exit third turbine 308 and undergo heat exchange in heattransfer unit 312 to form cooled oxygen gas stream 332 and recoveredheat energy 324′. Recovered heat energy 324′ from heat recovery unit 312can be transferred to steam generation unit 106. As shown in FIG. 3,recovered heat energy 324′ is combined with recovered heat energy 324,however, it should be understood that heat energy 324′ can be providedseparately to steam generation unit 106. Cooled hydrogen gas stream 322and cooled oxygen-rich gas stream can have a final temperature at ornear ambient temperatures, for example, a temperature from 20 to 30° C.,or 25° C. While heat transfer unit 312 is shown as one unit more thanone unit may be necessary to maintain sufficient temperature differencefor heat transfer. For example, heat transfer unit 312 can include oneor more heat exchangers with each heat exchanger performing heatexchange with hot hydrogen stream 318 and hot oxygen stream 328 toproduce cooled hydrogen stream 322 and cooled oxygen-rich stream 332, ormultiple heat exchangers arranged in series or parallel. Cooled hydrogengas stream 314 can be used in downstream chemical process, stored,transported, or sold. Cooled oxygen gas stream 318 can be used indownstream chemical processes and/or transportation units, stored,transported, or sold. Produced electrical energy 320 and 330 can be usedto power the electrolysis unit 102, combined with electrical energy 118,or used to power other equipment requiring electrical energy.

C. Solar-Powered System with a Solar-Powered Steam Turbine Unit

In some aspects of the invention, solar-powered system 400 includes afirst turbine that converts heat into electrical power. Referring toFIG. 4, the solar-powered turbine unit 106 can include first turbine200, solar unit 202, boiler 402, condenser 404, and pump 406. In system400, first turbine 200 is a steam powered turbine. Solar unit 202 can bea high-temperature solar collector for sunlight collection that iscapable of providing sufficient heat to heat water in boiler 402 to 300to 600° C. at 20 to 200 bar of pressure.

Pump 406 pumps water steam 408 from condenser 404 into boiler 402. Pump406 pressurizes water stream 408 such that it enters the boiler 402 as ahigh pressure water stream 410. In boiler 402, high pressure waterstream 410 is heated by solar heat energy 208 and, optionally, by thethermal heat energy 322 (See, for example, heat recovery systemdescribed in FIG. 3), to a temperature that vaporizes the water to formsteam, which is provided to other units as steam feed 210 and steam feed108. In a preferred aspect, the generated steam is high pressure steam.The boiler 402 can be any conventional solar boiler. In some instances,the boiler 402 can be a series of boilers such as when the first boilerconverts pumped water to saturated steam and then subsequently, a secondboiler heats the steam beyond its saturation temperature to producesuperheated steam.

A portion of the steam feed, steam feed 210, can exit boiler 402 andenter first turbine 200. First turbine 200 expands steam 210 to generatemechanical energy 120 and low pressure expanded steam 212. Mechanicalenergy (shaft work) 120 can be provided to first generator 104, whichgenerates and supplies electrical power 118 to electrolysis unit 102.Expanded steam 212 can exit the first turbine 200 and enter condenser404. In condenser 404, expanded steam 212 is cooled at a constantpressure to condense the steam to water. In some embodiments, the steam212 is cooled to a temperature and pressure to produce saturated steam.A portion of the generated steam, steam feed 108, exits boiler 402 andenters electrolysis unit 202. The amount of steam provided to theelectrolysis unit 102 can be regulated by a valve 412. As shown in FIG.4, all the heat and electrical energy needed to run the electrolysisunit 102 is provided without the use of fossil fuel, and thus no carbondioxide is generated during use. In some embodiments, cooling unit 302is not used.

D. Solar-Powered System with a Solar-Powered Gas Turbine Unit

In some aspects of the invention, the solar-powered turbine unit 106includes a solar-powered gas turbine using a suitable working fluid suchas air or carbon dioxide. FIG. 5 depicts a schematic of a solar-poweredsystem 500 that includes first turbine 200 in combination with the firstgenerator 104, electrolysis unit 102, solar unit 202, steam generationunit 204, and cooling unit 302. As shown in FIG. 5, first turbine 200 isa gas turbine. First turbine 200 provides mechanical energy 120 togenerator 104, which produces electrical power 118 that is supplied toelectrolysis unit 102. The electrolysis unit 102 produces the hydrogengas stream 110 and the oxygen-rich gas stream 112 as describedthroughout this Specification. For example, oxygen-rich gas stream is amixture of compressed air stream 116 and oxygen generated inelectrolysis unit 102. As previously described, the generated hydrogengas stream 110 and/or the oxygen-rich gas stream 112 is expanded throughthe turbines 304 and 308 and the expanded gases undergo heat exchange asthey pass through the heat transfer unit 312. The recovered heat 324,324′ from the heat transfer unit 312 can be transferred to the steamgeneration unit 204 and used as a source of heat in the generation ofsteam in System 500.

In system 500, solar unit 106 includes first turbine 200, steamgeneration unit 204 and solar units 202. Steam generation unit 204 canbe a heat recovery steam generation unit capable of recovering heat frommore than one source and producing steam. Steam generation unit 204 caninclude any pumps and/or water inlets and outlets necessary to providesufficient steam (e.g., high pressure steam) to electrolysis unit 102.As shown in FIG. 5, steam generation unit 204 includes first heatexchanger 502, which receives heated fluid 504 (for example, heated airor carbon dioxide) from first turbine 200. Heated fluid 504 can be usedas a working fluid in first heat exchanger 502 to provide heat for steamgeneration from water. Although only one heat exchanger is shown insteam generation unit 204, one or more heat exchangers can be used tomaintain sufficient heat exchange. For example, steam generation unit204 can have one or more shell and tube heat exchangers. Steam 208generated in steam generation unit 204 exits and enters electrolysisunit 102, where it is subjected to conditions sufficient toelectrolytically dissociate the steam into hydrogen and oxygen.

Partially cooled fluid 506 exits heat exchanger 502 and enterscompressor 508. In compressor 508, the partially cooled fluid 506 iscompressed to form compressed fluid 510. Compressed fluid 510 exitscompressor 508 at a pressure of 1 to 20 bar, and enters second heatexchanger unit 512. The compressed air can have a temperature of about250 to 300° C. upon entering second heat exchanger unit 512. Second heatexchanger unit 512 can include one or more heat exchangers. As shown inFIG. 5, second heat exchanger unit 512 includes three heat exchangers514, 516 and 518. Heat exchangers 514, 516 and 518 are coupled to solarunits 202. Solar units 202 can include multiple solar collectors,mirrors and lens that collect solar heat at sufficiently hightemperatures near 500° C. to greater than 1000° C., and provide the heatto each of heat exchangers 514, 516 and 518. Solar units 202 are capableof providing a desired amount of heat to heat exchangers 514, 516 and518. For example, as compressed fluid 510 passes through heat exchangers514, 516 and 518, the compressed fluid is heated progressively in eachheat exchanger until a temperature of the compressed fluid is about 720to 1350° C. at a pressure of 1 to 20 bar. Hot compressed fluid 520 exitsthe heat exchanger unit 514 and enters first turbine 200. In firstturbine 200, hot compressed air 520 is sufficiently expanded to generatemechanical energy 120, which is provided to the first generator 104 andthe compressor 508. Hot exhaust stream 504 exits first turbine 200 andenters heat exchanger 502 to continue the thermodynamic cycle. As shownin FIG. 5, the combination of the first heat exchanger 502, thecompressor 508, heat exchanger 514, and first turbine 200 can constitutea closed Brayton cycle; however other thermodynamic heat recovery cyclescan be used. In some embodiments, a portion or all of compressed fluid510 may be at a sufficient temperature that heat exchanger unit 512 isnot necessary, thus compressed fluid stream 510′ may be sent directly tofirst turbine 200. A portion of compressed fluid 510 flow can beregulated by valve 522. Solar powered turbine unit 106 as described forsystem 500 provides a thermally efficient “green” system to produce theenergy required for electrolysis of water with minimal to no generationof carbon dioxide emissions.

E. Solar-Powered Combined Cycle System

In some embodiments, a solar-powered combined cycle system can be usedto generate steam and electricity for the electrolysis unit 102. FIGS. 6and 7 depict schematics of the solar-powered combined cycle streamsystem 600. System 600 incudes the features of the solar powered turbinesystem described in FIG. 5 in combination with a back-pressure steamturbine 602. Referring to FIG. 6, back-pressure steam turbine 602 isused to provide additional mechanical energy to first generator unit104. The back-pressure steam turbine 602 receives steam feed 604 fromsteam generation unit 204. Steam feed 604 can be generated in steamgeneration unit 204 as described throughout this Specification.Expansion of steam feed 604 in back-pressure steam turbine 602 generatesadditional mechanical energy 606 that can be provided to power generatorunit 104. Expanded steam stream 608 exits the back-pressure steamturbine 602 and enters the electrolysis unit 102 to be used as a sourceof heated water in the generation of hydrogen and oxygen. In someembodiments, expanded steam stream 608 is mixed with steam feed 108entering the electrolysis unit 102.

Referring to FIG. 7, solar-powered system 700 includes back-pressuresteam turbine 702 and fourth generator unit 704 in combination withsolar heat generation unit 106, first generator unit 104, electrolysisunit 102, and cooling unit 300. Back-pressure steam turbine 702 providesmechanical energy to fourth generator unit 704, which then generateselectrical energy 706 for electrolysis unit 102. A portion of steam feed108, steam feed 708, is used in back-pressure steam turbine 702. Steamfeed 708 is expanded in steam generation unit 204 to produce mechanicalenergy 710 and hot expanded steam 712, which can be used as water sourcein electrolysis unit 102. As shown in FIG. 7, hot expanded steam 712 iscombined with steam feed 108 prior to entering electrolysis unit 102. Itshould be understood that hot expanded steam 712 can be provideddirectly to electrolysis unit. In some embodiments, cooling unit 302 isnot used in the systems 600 and 700 depicted in FIGS. 6 and 7. Thecombined cycle power generation systems described in FIGS. 6 and 7provides a thermally efficient, and novel “green” system to produce theenergy required for water-splitting reactions without generating carbondioxide emissions.

F. Method of Making Hydrogen Gas and Oxygen Gas

Hydrogen gas and oxygen gas can be produced from water using systems 100through 700 described throughout this specification. In one non-limitingmethod, water in the form of steam can be provided from solar-poweredturbine unit 106 to the electrolysis unit 102. The steam can be producedusing the systems 400 through 700 described in Sections C-E of thisspecification. In electrolysis unit 102, the steam is subjected toconditions sufficient to generate hydrogen and oxygen. In someembodiments, the hydrogen and oxygen can be collected individually inthe electrolysis unit 102 and/or collected as one gas stream andseparated in a unit coupled to the electrolysis unit. The hydrogen gas,the oxygen gas, or both can be provided to one or more storage units,chemical processing units, transportation units, or any combinationthereof. Since no fossil fuel is used to generate electricity in systems100 to 700 and no carbon-based feed stocks are use, the system generatesminimal or no carbon dioxide.

The systems 100 to 700 can be automated with suitable sensors and/orthermocouples to acquire data during the process. The acquired data canbe transmitted to one or more computer systems. The computer systems caninclude components such as CPUs or applications with an associatedmachine readable medium or article which may store an instruction or aset of instructions that, if executed by a machine, may cause themachine to perform a method and/or operations in accordance with themethods of the present invention. For example, upon input of data fromthe sensors and/or thermocouples, the flow of the fluids, opening orclosing of valves associated with the inlets and outlets for the variousturbines, compressors, heat exchangers, generators, electrolysis unit,etc. can be controlled. Such a machine may include, for example, anysuitable processing platform, computing platform, computing device,processing device, computing system, processing system, computer,processor, or the like, and may be implemented using any suitablecombination of hardware and/or software. The machine-readable medium orarticle may include, for example, any suitable type of memory unit,memory device, memory article, memory medium, storage device, storagearticle, storage medium and/or storage unit, for example, memory,removable or non-removable media, erasable or non-erasable media,writeable or re-writeable media, digital or analog media, hard disk,floppy disk, Compact Disk Read Only Memory (CD-ROM), Compact DiskRecordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk,magnetic media, magneto-optical media, removable memory cards or disks,various types of Digital Versatile Disk (DVD), a tape, a cassette, orthe like. The instructions may include any suitable type of code, suchas source code, compiled code, interpreted code, executable code, staticcode, dynamic code, and the like. The instructions may be implementedusing any suitable high-level, low-level, object-oriented, visual,compiled and/or interpreted programming language, such as C, C++, Java,BASIC, Perl, Matlab, Pascal, Visual BASIC, assembly language, machinecode, and so forth. The computer system may further include a displaydevice such as monitor, an alphanumeric input device such as keyboard,and a directional input device such as mouse.

EXAMPLES

The present invention will be described in greater detail by way ofspecific examples. The following examples are offered for illustrativepurposes only, and are not intended to limit the invention in anymanner. Those of skill in the art will readily recognize a variety ofnoncritical parameters which can be changed or modified to yieldessentially the same results.

Prophetic Example 1 Calculations Demonstrating Efficiency of a SolarPowered System with a Solar-Powered Gas Turbine Unit

Calculations to demonstrate the efficacy and benefits of the inventionare presented below with reference to FIG. 8. FIG. 8 is a schematic ofthe solar-powered turbine unit of the present invention that includes aclosed-loop gas turbine unit and is a simplified schematic of FIG. 5.

A total of 214.82 kWh solar energy is collected by solar units 202. Inheat exchangers 514, 516, and 518 coupled to solar units 202, thosesolar energy are further transferred to the working fluid. Considering a50% efficacy in the heat exchanges, the thermal energy carried by fluid520 is:

214.82 kWh×50%=120.91 kWh  (IV)

Fluid 520 enters the first turbine 200, where the hot compressed air 520is sufficiently expanded to generate mechanical energy 120. Assuming an80% of gas turbine efficiency, the total amount of energy in stream 120can be calculated as:

120.91 kWh×80%=96.73 kWh  (V)

The mechanical energy in stream 120 is provided to the first generator104 and the compressor 508 at a ratio of 85% to 15%, respectively. Withthat, the mechanical energy provided to the first generator 104 is:

96.73 kWh×85%=82.22 kWh  (VI)

Normally an electric generator has an efficiency about 90%. Thus, theelectrical power 118 produced is:

82.22 kWh×90%=74 kWh  (VII)

The electrical power 118 finally goes into the electrolysis unit 102.For a simplest case, we assume that 18 kg water in stream 108 directlyenters electrolysis unit 102. With the water and the electrical power,hydrogen and oxygen gas are produced in the electrolysis unit 102. Alower heating value (LHV) of hydrogen, 33.31 kWh/kg, and a 90%efficiency of electrolysis are used to calculate the amount of hydrogengenerated:

74 kWh×90%/33.31 kWh/kg=2 kg  (VIII)

Finally, the amount of oxygen generated can be quantified based on thechemical reaction of water-splitting given in Equation (III) and themolecular weight of each chemical component:

(2 kg/0.2 g/mol)×0.5×32 g/mol=16 kg  (IX)

In summary of this example, by using the invented method, a total of214.82 kWh solar energy and 18 kg water are used to produce 2 kghydrogen gas and 16 kg oxygen gas. Note that there is no carbon dioxideformed in the entire process. As a simple comparison, if we produce thesame amount of hydrogen and oxygen gas using thermochemical splitting ofwater, where the energy supply is not solar but fossil fuels of naturalgas, then about 117 pounds of CO₂ will be generated; if the energysupply is gasoline, then about 157 pounds of CO₂ will be generated; ifthe energy supply is coal (lignite), then about 215 pounds of CO₂ willbe generated.

1. A solar-powered system for generating hydrogen gas and oxygen gasfrom water, the system comprising: (a) an electrolysis unit configuredto produce hydrogen gas and oxygen gas from water, the electrolysis unitcomprising a steam feed inlet and at least a first product outlet forhydrogen gas, oxygen gas or both; (b) a first generator unit configuredto provide electricity to the electrolysis unit; (c) a solar-poweredturbine unit configured to drive the first generator unit and to supplysteam to the steam feed inlet, the solar-powered turbine unitcomprising: (i) a first turbine coupled to and configured to provideshaft work to the first generator unit; (ii) a steam generation unitcoupled to the steam feed inlet of the electrolysis unit and configuredto hold water; and (iii) a solar unit configured to generate and provideheat to the steam generation unit; and (d) a product cooling unitcoupled to the electrolysis unit and configured to receive and reducethe temperature of the produced hydrogen gas or oxygen gas, or both 2.(canceled)
 3. The system of claim 1, wherein the product cooling unitcomprises: (i) a second turbine coupled to and configured to providepower to a second generator unit, wherein the second turbine isconfigured to receive the produced hydrogen gas or oxygen gas, or,preferably, both; and (ii) a heat transfer unit coupled to andconfigured to transfer heat produced from the product cooling unit tothe steam generator unit.
 4. The system of claim 3, wherein the secondgenerator unit is configured to provide electricity to the electrolysisunit.
 5. The system of claim 4, wherein the product cooling unitcomprises a third turbine coupled to and configured to provide power tothe second generator unit or to a third generator unit, wherein thethird turbine is configured to receive the produced hydrogen gas oroxygen gas, or, preferably, both, and wherein the third generator unitis configured to provide electricity to the electrolysis unit.
 6. Thesystem of claim 1, wherein the solar powered turbine unit comprises: (i)the first turbine coupled to and configured to provide shaft work to thefirst generator unit; (ii) the steam generation unit coupled to thesteam feed inlet of the electrolysis unit, wherein the steam generationunit comprises a boiler that is configured to hold water and producesteam; (iii) the solar unit configured to generate and provide heat tothe boiler; and (iv) a condenser; wherein the boiler is coupled to thefirst turbine and configured to transfer steam from the boiler to thefirst turbine, wherein the first turbine is coupled to the condenser andconfigured to transfer steam from the turbine to the condenser, whereinthe condenser is configured to condense the steam transferred from theturbine into liquid, and wherein the condenser is coupled to andconfigured to transfer the liquid to the boiler.
 7. The system of claim1, wherein the solar powered turbine unit is a closed-loop gas turbineunit comprising: (i) the first turbine coupled to and configured toprovide shaft work to the first generator unit; (ii) the steamgeneration unit coupled to the steam feed inlet of the electrolysisunit, wherein the steam generation unit comprises a first heat exchangercoupled to the first turbine to receive heated fluid from the firstturbine, wherein heat is transferred in the first heat exchanger fromthe heated fluid to water to produce steam and cooled fluid; and (iii)the solar unit configured to generate and provide heat to the cooledfluid; and wherein the heat exchanger is coupled to a compressor andconfigured to transfer the cooled fluid to the compressor, wherein thecompressor is coupled to a second heat exchanger that is configured toheat the cooled fluid with heat produced by the solar unit, and whereinthe second heat exchanger is coupled to the first turbine to transferthe heated fluid to the first turbine.
 8. The system of claim 7, furthercomprising a back pressure steam turbine unit, wherein the back pressuresteam turbine is coupled to the first heat exchanger and configured toreceive steam from the heat exchanger.
 9. The system of claim 8, whereinthe back pressure steam turbine unit comprises a fourth turbine coupledto and configured to provide shaft work to the first generator unit. 10.The system of claim 8, wherein the back pressure steam turbine unitcomprises a fourth turbine coupled to and configured to provide power toa fourth generator unit, and wherein the fourth generator unit isconfigured to provide electricity to the electrolysis unit.
 11. Thesystem of claim 1, wherein the steam produced by the steam generationunit is pressurized steam.
 12. The system of claim 1, wherein the systemdoes not produce carbon dioxide during use.
 13. The system of claim 1,wherein the produced hydrogen gas or the produced oxygen gas, or both,are each used in a downstream chemical process.
 14. The system of claim1, wherein the electrolysis unit comprises at least two product outlets,wherein the first product outlet is for hydrogen gas and a secondproduct outlet is for oxygen gas.
 15. The system of claim 14, furthercomprising an air supply coupled to the electrolysis unit, wherein theair supply provides air to an oxygen evolution side of the electrolysisunit such that a mixture of oxygen and air are produced from the secondoutlet.
 16. A method of generating hydrogen gas and oxygen gas fromwater with the system of claim 1, the method comprising subjecting waterto electrolysis conditions sufficient to produce hydrogen gas and oxygengas.
 17. The method of claim 16, further comprising providing thehydrogen gas to one or more storage units, chemical process units,transportation units, or any combination thereof, and/or providing theoxygen gas to one or more storage units, chemical process units,transportation units, or any combination thereof.
 18. The method ofclaim 16, wherein the produced hydrogen gas or the produced oxygen gas,or both, are each used in a downstream chemical process.
 19. The methodof claim 16, wherein no carbon dioxide is produced by the system. 20.The method of claim 16, wherein the water is in the form of steamproduced by the steam generation unit.